Conditionally enable functionality with feature flags

.cirrus.yml

@@ -20,6 +20,8 @@ build: &BUILD
     - $TOOL +$TOOLCHAIN $BUILD $ZFLAGS --target $TARGET --all-targets
     - $TOOL +$TOOLCHAIN doc $ZFLAGS --no-deps --target $TARGET
     - $TOOL +$TOOLCHAIN clippy $ZFLAGS --target $TARGET -- $CLIPPYFLAGS
+    - if [ -z "$NOHACK" ]; then $TOOL install cargo-hack; fi
+    - if [ -z "$NOHACK" ]; then $TOOL hack $ZFLAGS check --target $TARGET --each-feature; fi
 
 # Tests that do require executing the binaries
 test: &TEST
@@ -50,14 +52,16 @@ task:
     - cargo build --target i686-unknown-freebsd
     - cargo doc --no-deps --target i686-unknown-freebsd
     - cargo test --target i686-unknown-freebsd
+  i386_feature_script:
+    - . $HOME/.cargo/env
+    - cargo hack check --each-feature --target i686-unknown-freebsd
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
 # Test OSX in a full VM
 task:
-  matrix:
-    - name: OSX x86_64
-      env:
-        TARGET: x86_64-apple-darwin
+  name: OSX x86_64
+  env:
+    TARGET: x86_64-apple-darwin
   osx_instance:
     image: catalina-xcode
   setup_script:
@@ -192,13 +196,17 @@ task:
     # https://github.com/rust-embedded/cross/issues/535
     - name: iOS aarch64
       env:
+        # cargo hack tries to invoke the iphonesimulator SDK for iOS
+        NOHACK: 1
         TARGET: aarch64-apple-ios
         # Rustup only supports cross-building from arbitrary hosts for iOS at
         # 1.49.0 and above.  Below that it's possible to cross-build from an OSX
         # host, but OSX VMs are more expensive than Linux VMs.
         TOOLCHAIN: 1.49.0
     - name: iOS x86_64
       env:
+        # cargo hack tries to invoke the iphonesimulator SDK for iOS
+        NOHACK: 1
         TARGET: x86_64-apple-ios
         TOOLCHAIN: 1.49.0
     # Cross testing on powerpc fails with "undefined reference to renameat2".
@@ -222,6 +230,8 @@ task:
         TARGET: x86_64-unknown-netbsd
     - name: Redox x86_64
       env:
+        # cargo-hack needs a newer compiler
+        NOHACK: 1
         TARGET: x86_64-unknown-redox
         # Redox requires a nightly compiler.
         # If stuff breaks, change nightly to the date in the toolchain_*
@@ -269,6 +279,6 @@ task:
     image: rustlang/rust:nightly
   setup_script:
     - cargo update -Zminimal-versions
-  script:
+  check_script:
     - cargo check
   before_cache_script: rm -rf $CARGO_HOME/registry/index

CHANGELOG.md

@@ -3,6 +3,17 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
+## [Unreleased] - ReleaseDate
+### Added
+
+- Added fine-grained features flags.  Most Nix functionality can now be
+  conditionally enabled.  By default, all features are enabled.
+  (#[1498](https://github.com/nix-rust/nix/pull/1498))
+
+### Changed
+### Fixed
+### Removed
+
 ## [0.23.0] - 2021-09-28
 ### Added
 

Cargo.toml

@@ -10,6 +10,7 @@ categories  = ["os::unix-apis"]
 include = ["src/**/*", "LICENSE", "README.md", "CHANGELOG.md"]
 
 [package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]
 targets = [
   "x86_64-unknown-linux-gnu",
   "aarch64-linux-android",
@@ -32,6 +33,48 @@ cfg-if = "1.0"
 [target.'cfg(not(target_os = "redox"))'.dependencies]
 memoffset = "0.6.3"
 
+[features]
+default = [
+  "acct", "aio", "dir", "env", "event", "features", "fs",
+  "hostname", "inotify", "ioctl", "kmod", "mman", "mount", "mqueue",
+  "net", "personality", "poll", "process", "pthread", "ptrace", "quota",
+  "reboot", "resource", "sched", "signal", "socket", "term", "time",
+  "ucontext", "uio", "users", "zerocopy",
+]
+
+acct = []
+aio = []
+dir = ["fs"]
+env = []
+event = []
+features = []
+fs = []
+hostname = []
+inotify = []
+ioctl = []
+kmod = []
+mman = []
+mount = ["uio"]
+mqueue = ["fs"]
+net = ["socket"]
+personality = []
+poll = []
+pthread = []
+ptrace = ["process"]
+quota = []
+process = []
+reboot = []
+resource = []
+sched = ["process"]
+signal = ["process"]
+socket = []
+term = []
+time = []
+ucontext = ["signal"]
+uio = []
+users = ["features"]
+zerocopy = ["fs", "uio"]
+
 [target.'cfg(target_os = "dragonfly")'.build-dependencies]
 cc = "1"
 

src/dir.rs

@@ -5,6 +5,7 @@ use std::os::unix::io::{AsRawFd, IntoRawFd, RawFd};
 use std::ptr;
 use std::ffi;
 use crate::sys;
+use cfg_if::cfg_if;
 
 #[cfg(target_os = "linux")]
 use libc::{dirent64 as dirent, readdir64_r as readdir_r};
@@ -186,34 +187,24 @@ pub enum Type {
 
 impl Entry {
     /// Returns the inode number (`d_ino`) of the underlying `dirent`.
-    #[cfg(any(target_os = "android",
-              target_os = "emscripten",
-              target_os = "fuchsia",
-              target_os = "haiku",
-              target_os = "illumos",
-              target_os = "ios",
-              target_os = "l4re",
-              target_os = "linux",
-              target_os = "macos",
-              target_os = "solaris"))]
-    pub fn ino(&self) -> u64 {
-        self.0.d_ino as u64
-    }
-
-    /// Returns the inode number (`d_fileno`) of the underlying `dirent`.
-    #[cfg(not(any(target_os = "android",
-                  target_os = "emscripten",
-                  target_os = "fuchsia",
-                  target_os = "haiku",
-                  target_os = "illumos",
-                  target_os = "ios",
-                  target_os = "l4re",
-                  target_os = "linux",
-                  target_os = "macos",
-                  target_os = "solaris")))]
     #[allow(clippy::useless_conversion)]    // Not useless on all OSes
     pub fn ino(&self) -> u64 {
-        u64::from(self.0.d_fileno)
+        cfg_if! {
+            if #[cfg(any(target_os = "android",
+                         target_os = "emscripten",
+                         target_os = "fuchsia",
+                         target_os = "haiku",
+                         target_os = "illumos",
+                         target_os = "ios",
+                         target_os = "l4re",
+                         target_os = "linux",
+                         target_os = "macos",
+                         target_os = "solaris"))] {
+                self.0.d_ino as u64
+            } else {
+                u64::from(self.0.d_fileno)
+            }
+        }
     }
 
     /// Returns the bare file name of this directory entry without any other leading path component.